Stabilizer composition for lessening early discoloration of polyvinyl chloride resins when heated



United States Patent 3,507,827 STABILIZER COMPOSITION FOR LESSENINGEARLY DISCOLORATION OF POLYVINYL CHLDRIDE RESINS WHEN HEATED Mark W.Pollock, Teaneck, N.J., assig'nor to Argus Chemical Corporation,Brooklyn, N.Y., a corporation of Delaware No Drawing.Continuation-impart of application Ser. No. 417,513, Dec. 10, 1964,which is a continuation-in-part of application Ser. No. 336,887, Jan.10, 1964. This application Jan. 27, 1967, Ser. No. 612,107

Int. Cl. C08f 45/58 U.S. Cl. 26045.75 17 Claims ABSTRACT OF THEDISCLOSURE A stabilizer combination is provided for decreasing earlydiscoloration of polyvinyl chloride resins when heated at 350 F. andhigher, including 1) a dialkyl, dicycloalkyl or alkylcycloalkyl tinmercapto carboxylic acid ester, and (2) an alphaor beta-mercapto acidhaving at least three carbon atoms, or an alphaor betamercapto alcoholhaving at least two carbon atoms. A typical combination is composed ofdibutyltin diisooctyl thioglycollate and thiolactic acid.

Polyvinyl chloride resin compositions are also provided containing thesestabilizers, and a process for improving the resistance of such resinsto the development of early discoloration during the first thirtyminutes of heating by incorporating these stabilizers therein.

This application is a continuation-in-part of application Ser. No.417,513, filed Dec. 10, 1964, and now U.S. Patent No. 3,398,114 which inturn is a continuation-inpart of application Ser. No. 336,887, filedJan. 10, 1964, and now abandoned.

This invention relates to homogeneous liquid polyvinyl chloride resinstabilizer compositions containing an organotin mercapto acid ester andan alphaor betamercapto alcohol and/ or acid, and to polyvinyl chlorideresin compositions containing these compounds and having as a result animproved resistance to development of disocloration during heating, andto a process for improving the resistance of polyvinyl chloride resinsto early discoloration when heated, using such compounds.

Organ-otin mercapto acid esters are now recognized as being among themost effective stabilizers for inhibiting the degradation of polyvinylchloride resins at the high temperatures, e.g. 350 F. or 375 F., towhich they are subjected during working. Although these compounds havebeen successful in providing good stability for one hour or more at 350F. to 375 F., many of these compounds impart or do not entirely preventan early yellow discoloration to the resin, which is manifested beforesevere heat deterioration really sets in. This early discoloration hasnot been considered disadvantageous for many uses, and the eiforts ofmost workers in this field have been directed towards minimizing theonset of the more serious heat deterioration which sets in during longheating, as in milling. However, because of this discoloration and theaccompanying haziness or cloudiness that may also appear, it has notbeen possible in all cases to obtain a substantially clear and colorlesspolyvinyl chloride resin composition.

Some organotin compounds can impart, in addition, an initial haziness orcloudiness to the resin. The organotin mercapto acid esters are perhapsless subject to this defect than other organotin compounds, but clarityis also deleteriously affected by other additives. When other additivesare present which are themselves responsible for an initial haziness,even these organotin compounds are not capable of alleviating oreliminating the condition. The problem of lack of clarity is especiallytroublesome with lubricants and impact modifiers, which tend tocontribute to this initial lack of clarity, or cloudiness, and also insome cases to the initial discoloration of the resin.

Although early discoloration and any accompanying cloudiness are notnearly so intense as later discoloration and embrittlement arising fromheat deterioration of the resin, it has been recognized that the earlydiscoloration arising during the first fifteen to thirty minutes ofheating afiects a relatively greater proportion of the resin. This isbecause' the average period of time during which a given amount of resinproduct remains in the processing equipment, even in a continuousprocess which includes recycling of portions of the worked product, isless than thirty minutes. Only a minor portion of the resin will besubjected to working temperatures for periods of up to one hour orlonger. Hence, the preservation of a good color and clarity during thefirst thirty minutes of heating can be more difficult than theprotection of the relatively small proportion of the resin by long termheat stabilizers, such as the organotin mercapto acid esters.

Although the problem of minimizing early discoloration is of longstanding, no one has been able to suggest a solution of it.

In fact, there has only been one patent that has suggested a stabilizercombination capable of minimizing initial color and retaining initialclarity along with good long term stability, and this patent is directedto a nonorganotin-containing stabilizer combination. U.S. Patent No.2,997,454, patented Aug. 22, 1961, to Leistner, Hecker and Knoepke, hassuggested the combination with heavy metal salts of a higher fatty acidand organic triphosphites, or with such phosphites and polyvalent metalsalts of hydrocarbon-substituted phenols, of an acid phosphorus compoundhaving at least one acidic hydrogen atom attached through oxygen tophosphorus. This type of compound is not useful with organotin compoundsto minimize early discoloration.

Combinations of various types of additives with organotin compounds havebeen proposed to improve their heat stabilizing effectiveness, and toimpart special efifects. For example, U.S. Patent No. 2,914,506 to Macket al., dated Nov. 24, 1959, suggests combinations of organotinthioglycollates with metallic and non-metallic stabilizers, includingmetal salts, epoxy compounds, phosphites and phenols. U.S. Patent No.2,938,013 to Mack et al., dated May 24, 1960, discloses combinations oforganotin half ester maleates with other organotin compounds, metalsalts, phosphites and epoxy compounds. Lazcano British Patent No.1,008,589, published Oct. 27, 1965, discloses combinations of organotinhalf ester maleates and thioglycollates with other metal salts, phenols,epoxy compounds, phosphites, and polyols. None of these combinations iseffective both to minimize early discoloration and preserve clarity.

French Patent No. 1,440,654, published Apr. 25, 1966 (the correspondingU.S. application Ser. No. 417,513 of which this application is acontinuation-in-part) describes combinations of an organotin moiety, amercapto acid moiety, and an antioxidant. The organotin moiety can,inter alia, include organotin maleate half esters, and the antioxidantsinclude phenols, thiodipropionates, monoand polysulfides, phosphites,and aromatic amines.

British Patent No. 1,001,344, published Aug. 18, 1965, describesstabilizer compositions composed of (a) an organo metallic compound inwhich the metal atom is lithium, sodium, potassium, magnesium, calcium,zinc, strontium, cadmium, barium, aluminum, tin or lead, or a mixture ofany two or three of such organic-metallic compounds, provided that thestabilizer does not solely comprise barium laurate or cadmium laurate ordibasic lead phthalate, nor contain a mixture comprising organic-barium,organic-cadmium or organic-tin compounds; (b) a sulfur-containingorganic or organo-metallic compound having a boiling point atatmospheric pressure not below 200 C., and that does not contain chainsof more than two consecutive sulfur atoms and in which at least one ofthe sulfur atoms has at least one lone electron pair, exceptingmercapto-benzimidazole, mercapto-benzothiazole and their salts; and (c)an organic antioxidant capable of inhibiting chain reactions leading todegradation in the chlorine-containing homopolymer or copolymer. Thesecompositions are not however indicated to improve resistance to earlydiscoloration.

US. Patent No. 3,067,166, to Zaremsky, dated Dec. 4, 1962, disclosescombinations of zinc or tin salts of organic acids and thioglycollicacid esters. British Patent No. 874,574 to Luz, published Aug. 10, 1961,describes stabilizer compositions composed of an organotin acid saltsuch as dibutyl tin diacetate and thioglycollic acid ester. Thesecompositions do not lessen early discoloration, because the esters areineffective in this respect. British Patent No. 771,857 published Apr.3, 1967, discloses combinations of mercapto acid esters with organotinoxides.

Wooten et al. US. Patent No. 3,063,963, issued Nov. 13, 1962, disclosecombinations of organotin carboxylates of monoor dicarboxylic acids withomega mercapto acid esters or omega mercapto alcohols to improveweathering resistance of polyvinyl chloride resins. There is nosuggestion that early discoloration is lessened in the combinations thatare disclosed.

It has now been found that combinations of an organotin mercaptocarboxylic acid ester and an alphaor beta-mercapto acid having at leastthree carbon atoms or alphaor beta-mercapto alcohol having at least twocarbon atoms have the unusual property of lessening development ofdiscoloration of polyvinyl chloride resins, particularly during thefirst thirty minutes of heating at 375 F. These combinations arehomogeneous liquids which can be readily measured and mixed into theresin, and are thus easy to formulate, market and use.

In accordance with this invention, there are provided stabilizercompositions for polyvinyl chloride resins comprising (a) at least oneorganotin mercapto acid ester which has from one to two mercaptocarboxylic acid ester groups linked to tin through a mercapto sulfuratom, and two alkyl and/or cycloalkyl groups linked to each tin throughcarbon, and (b) at least one mercapto compound selected from the groupconsisting of alphaand beta-mercapto carboxylic acids having from threeup to about thirty carbon atoms and alphaand beta-mercapto alcoholshaving from two to about thirty carbon atoms.

The mercapto acid or alcohol (b) alone imparts no stabilizing elTectupon polyvinyl chloride resins but in' combination with the organotinmercapto acid ester lessens or entirely prevents development of a yellowdiscoloration during heating at 350 F. The mercapto acid or mercaptoalcohol can also reduce any initial cloudiness and discoloration intheresin introduced by the organotin mercapto acid. ester and/orstabilizers and additives such as impact-modifiers and lubricants.

The organotin mercapto acid esters can be monomeric or polymeric, butare preferably monomeric. The monomers can be defined as organotincompounds having organic radicals linked to tin only through carbon,sulfur,

and oxygen, and having the general formula:

/Sn-[SZr-( O a) ml: R2 I R is an organic group derived from a monohydricor polyhydric alcohol having from one to about four hydroxyl groups andfrom about one to about thirty carbon atoms. If there is more than oneCOOR group, the R radicals can be the same or different.

R and R are alkyl or cycloalkyl radicals having from about three toabout thirty carbon atoms, preferably from three to seven. R and R can,for example, be propyl, isopropyl, n-butyl, isobutyl, tert-butyl, amyl,hexyl, octyl, isononyl, monyl, decyl, undecyl Z-ethylhexyl, iso-octyl,lauryl, palmityl, stearyl, myristyl, behenyl, cyclobutyl, cyclohexyl,methyl cyclohexyl and cyclopentyl.

'Z is a bivalent organic radical carrying the S and COOR groups, and inaddition can contain halogen, free carboxylic acid groups, keto groups,mercapto groups, carboxylic acid salt groups, ether groups and hydroxylgroups. The Z radical has from one to about thirty carbon atoms, such asan alkylene, arylene or cycloalkylene radical,

The S--Z (COOR groups are derived from monoor polymercapto carboxylicacid esters by removal of the hydrogen atom of the mercapto group. Theseinclude the esters of aliphatic, aromatic, cycloaliphatic andheterocyclic acids which contain at least one mercapto group, and canalso contain inert substituents such as halogen, hydroxyl, keto andalkoxy groups, such as, for example, esters of mercaptoacetic acid,mercaptopropionic acid, mercaptooleic acid, mercaptoricinoleic acid,mercaptolinoleic acid, mercaptostearic acid, mercaptobutyric acid,mercaptovaleric acid, mercaptohexanoic acid, mercaptooctanoic acid,thiolactic acid, mercaptolevulinic acid, mercaptolauric acid,mercaptobehenic acid, dithiotartaric acid, mercaptopalmitic acid,mercaptobenzoic acid, mercaptomethylbenzoic acid, mercaptocyclohexanecarboxylic acid, mercaptofuric acid, thiomalic acid, mercaptoglutaric'aid, mercaptoaxelaic acid, mercaptomalonic acid, mercaptoadipic acid,mercaptopimelic acid, mercaptosuberic acid, mercaptosebacic acid, andmercaptoterphthalic acid.

R is an organic group derived from a monohydric or polyhydric alcohol ofthe formula R (OH),, where n; is an integer from one to about four, butis preferably one or two. Thus, R, can be alkyl, alkylene, alkylenyl,aryl, arylene, mixed alkyl-aryl, mixed aryl-alkyl, cycloaliphatic andheterocyclic and acn contain from about one to about thirty carbonatoms, and can also contain ester groups, alkoxy groups, hydroxylgroups, halogen atoms and other 'inert substituents. Preferably, R isderived from a monohydric alcohol containing from one to about thirtycarbons atoms, such as methyl, ethyl, propyl, n-butyl, t-butyl,isobutyl, octyl, isooctyl, Z-ethylhexyl, decyl, lauryl, octadecyl,myristyl, palmityl, oleyl, dodecyl, isotrodecyl and ricinoleyl alcohols,cyclic monohydric alcohols, such as cyclopropanol,2,2-dimethyl-l-cyclopropanol, cyclobutanol, 2-pheny1 1 cyclobutanol,cyclopentanol, cyclopentenol, cyclohexanol, cyclohexenol, 2- rnethyl-,3-methyl-, and 4-methyl-cyclohexanol, Z-phenylcyclohexanol,3,3,5-trirnethyl cyclohexanol, 1,4-cyclohexadiene 3 d, cyclohepta nol,cycloheptene-S-d, 1,5 cycloheptadiene-3-ol, 2-methyl-, 3-methyland4-methy1 cycloheptanol, cyclooctanol, cyclooctenol, cyclononanol,cyclodecanol, cyclodecene-3.-ol, cyclododecanol, the para-methanols,such as 3-hydroxy-p-menthane, 2-hydroxy-p-menthane, the para-menthenolssuch as ot-terpineol, borneol, pine oil, fenchol,2,2-di-methyl-3,6-endo-methylene cyclohexanol, methyl borneol,2,2,10-trimethyl 3,6 endomethylene cyclohexanol, the cyclicsesquiterphenols such as'farnesol and nerolidol, the sterols such ascholesterol, dihydrocholesterol, ergosterol, 24-ethyl cholesterol, thecondensed alicyclic alcohols such as 1-, and Z-hydroxyl-l,2,3,4-tetrahydronaphthalene and 1-, and 2-hydroxydecahydronaphthalene,or from a dihydric alcohol such as glycols containing from two to aboutthirty carbon atoms, including ethylene glycol, propylene glycol,diethylene glycol, dipropylene glycol, tetramethylene glycol, neopentylglycol and decarnethylene glycol, 2',2'-4-trimethyl pentane-diol,2,2',4,4'-tetramethyl cyclobutane-diol, cyclohexane-1,4-dimethylanol,4,4 isopropylidene-dicyclhexanol, and polyols such as glycerine,triethylol propane, mannitol, sorbitol, erythritol, dipentaerythritol,pentaerythritol, and trimethylol propane.

These marcapto acid esters, where not known, can be readily prepared byreaction of the mercaptocarboxylic acid esters with the correspondingorganotin oxide or chloride. For a more complete explanation of theprocess for making, and for additional examples of these disorganotinmercapto ester compounds, see US. Patents Nos. 2,648,650 to Weinberg etal., 2,641,596 and 2,752,- 325 to Leistner, and 3,115,509 to Mack, andCanadian Patent No. 649,989 to Mack.

The organotin mercapto acid esters containing two different mercaptoacid ester groups can be prepared by reacting the desired organotinoxide or chloride with a mixture of the mercapto acid esters, or byheating the two different organotin esters together.

Polymeric organotin mercapto acid esters falling within the presentinvention are formed of a chain of organotin groups wherein each tinatom is linked to two alkyl and/ or cycloalkyl groups. There is at leastone mercapto carboxylic acid ester group attached through a sulfur atomto each terminal tin atom of the chain. The linking group between tinatoms of the chain can be any bivalent organic group linked to tinthrough oxygen or sulfur. One type of such polymeric organotinthioesters can be dewherein Z is a bivalent group, such as oxygen,sulfur, a mercapto acid group, or a mercapto alkanol group, and n is anumber from one to about twenty.

The Z mercapto acid group can have the formula:

SZ COO and the Z mercaptoalkanol group can have the formula:

SZ O

The following organotin thioesters are typical of those coming withinthe invention:

S-OHzCOO 04H: N W.

The second component is selected from the group consisting of 06- andfi-mercapto acids having from three to thirty carbon atoms and ocandfi-mercapto alcohols having from two to thirty carbon atoms. The andfl-mercaptohydroxy acids fall within both classes. These com- R R R Rand R are hydrogen or a hydrocarbon group, such as alkyl, aryl, orcycloalkyl, alkenyl or cycloalkenyl.

In addition, R or R or R, can be hydroxyalkyl. R and/or R can also be OHCOOH. In addition, R or R can be selected from (CH ),,COOH wherein n isfour or five, or M I HSOCOOH When R or R is (CH COOH, the other ishydrogen; when R or R is I use-coon the other is hydrogen. Furthermore,R R R and R of Formula IV can be taken together with to form a phenylring, a naphthyl ring, a cyclohexyl ring or a furfuryl ring, and R and Rof Formula III can be taken together with to form a phenyl ring.

The a-mercapto acids are preferred, and the ,8-rnercapto-acids are nextpreferred. The acids are preferred to the alcohols because of theirbetter odor.

Examples of these mercapto acids include: B-mercapto- 2,3-dimethylbutyric acid, Z-mercaptopropionic acid, 3- mercaptopropionic acid,Z-mercaptobutyric acid, 3-mercaptobutyric acid, 3-mercapto-4-hydroxybutyric acid, 2 mercapto 3 methylbutyric acid, 3-mercapto-4,5-dimethylhexanoic acid, 2 mercaptostearic acid, 3-mercapto-oleic acid,Z-mercapto-valeric acid, 3-mercaptohexanoic acid,Z-mercapto-6-hydroxy-hexanoic acid, 3- mercapto-4-ethylhexanoic acid,thiomalic acid, thiocitric acid, dithiotartaric acid, 3-mercaptoglutaricacid, 2-mercapto-pimelic acid, 2-mercaptosuberic acid, thiosalicyclicacid, Z-mercaptocyclohexane carboxylic acid, 3-mercapto- Z-naphthoicacid, 3-mercaptofuroic acid, and Z-mercaptolauric acid, and mixtures ofthese.

Typical mercapto alcohols include Z-mercaptoethanol,Z-mercapto-l-propanol, l-mercapto-Z-propanol, 3-mercapto4,5-dimethylhexanol, 2-mercapto-4-ethylhexanol, 2-mercapto-3-butanol,3-mercapto-lauryl alcohol, 3-mercapto-4,5-diethyl hexanol,2-mercapto-oleyl alcohol, 2- mercapto-stearyl alcohol,Z-mercapto-l-butanol, orthomercapto-benzyl alcohol,Z-mercaptocyclohexanol, and 3-mercapto-tetrahydrofurfuryl alcohol.

A unique property of these 00- and fl-mercapto acid and mercaptoalcohols is their excellent compatibility with the organotin mercaptoacid esters. These compounds are generally miscible throughout the rangeof proportions used for the invention, and such mixtures are homogeneousliquid solutions. Thus, they can be readily measured and blended into aresin mixture by the resin processor.

In this respect, the a-mercapto acid having two carbon atoms differs;thioglycollic acid is incompatible with organotin mercapto acid esters,and causes precipitation, forming a nonhomogeneous mixture. Anonhomogeneous mixture increases the problems of measuring and mixingthe stabilizer into the resin, and practically speaking is unmarketablecommercially, because of its dissolute appearance.

The invention is applicable to any polyvinyl chloride resin. The termpolyvinyl chloride as used herein is inclusive of any polymer formed atleast in part of the recurring group and having a chlorine content inexcess of In this group, the X groups can each be either hydrogen orchlo rine. In polyvinyl chloride homopolymers, each of the X groups ishydrogen. Thus, the term includes not only polyvinyl chloridehomopolymers but also after-chlorinated polyvinyl chlorides such asthose disclosed in British Patent No. 893,288 and also copolymers ofvinyl chloride in a major proportion and other copolymerizable monomersin a minor proportion, such as copolymers of vinyl chloride and vinylacetate, copolymers of vinyl chloride with maleic or fumaric acids oresters, and co polymers of vinyl chloride with styrene, propylene, andethylene. The invention also is applicable to mixtures of polyvinylchloride in a major proportion with other synthetic resins such aschlorinated polyethylene or a copolymer of acrylonitrile, butadiene andstyrene. Among the polyvinyl chlorides which can be stabilized are theuniaxially-stretch oriented polyvinyl chlorides described in US. PatentNo. 2,984,593 to Isaksem et al., that is, syndiotactic polyvinylchloride, as well as atactic and iso tactic polyvinyl chlorides.

The stabilizing combinations of this invention, both with and withoutsupplementary stabilizers, are excellent stabilizers for bothplasticized and unplasticized polyvinyl chloride resins. Whenplasticizers are to be employed, they may be incorporated into thepolyvinyl chloride resins in accordance with convention means. Theconventional plasticizers can be used, such as dioctyl phthalate,dioctyl sebacate and tricresyl phosphate. Where a plasticizer isemployed, it can be used in an amount within the range from to 100 partsby weight of the resin.

Particularly useful plasticizers are the epoxy higher esters having fromabout twenty to about one hundred fifty carbon atoms. Such esters willinitially have had unsaturation in the alcohol or acid portion of themolecule, which is taken up by the formation of the epoxy group.

Typical unsaturated acids are oleic, linoleic, linolenic, erucic,ricinoleic and brassidic acids, and these may be esterified with organicmonohydric or polyhydric alcohols, the total number of carbon atoms ofthe acid and the alcohol being within the range stated. Typicalmonohydric alcohols include butyl alcohol, 2-ethylhexyl alcohol, laurylalcohol, isooctyl alcohol, stearyl alcohol, and oleyl alcohol. The octylalcohols are preferred. Typical olyhydric alcohols includepentaerythritol, glycerol, ethylene glycol, 1,2 propylene glycol, 1,4butylene glycol, neopentyl glycol, ricinoleyl alcohol, erythritol,mannitol and sorbitol. Glycerol is preferred. These alcohols may befully or partially esterified with the epoxidized acid. Also useful arethe epoxidized mixtures of higher fatty acid esters found innaturally-occurring oils such as epoxidized soybean oil, epoxidizedolive oil, epoxidized cottonseed oil, epoxidized tall oil fatty acidesters, epoxidized coconut oil and epoxidized tallow. Of these,epoxidized soybean oil is preferred.

The alcohol can contain the epoxy group and have a long or short chain,and the acid can have a short or long chain, such as epoxy stearylacetate, epoxy stearyl stearate, glycidyl stearate, and polymerizedglycidyl methacrylate.

A small amount, usually not more than 1.5%, of a parting agent orlubricant, also can be included. Typical parting agents are the higheraliphatic acids, and salts having twelve to twenty-four carbon atoms,such as stearic acid, lauric acid, palmitic acid and myristic acid,lithium stearate and calcium palmitate, mineral lubricating oils,polyvinyl stearate, polyethylene and paraffin wax.

Impact modifiers, for improving the toughness or impact-resistance ofunplasticized resins, can also be added to the resin compositionsstabilized by the present invention in minor amounts of usually not morethan 10%. Examples of such impact modifiers include chlorinatedpolyethylene, ABS polymers, and polyacrylate-butadiene graft copolymers.

The stabilizer components of the invention including the organotinmercapto acid ester and ocand B-mercapto acid or alcohol, are employedin an amount sufiicient to impart the desired resistance to heatdeterioration at working temperatures of 350 F. and above. The morerigorous the conditions to which the resin will be subjected duringworking and mixing, and the longer the term required for resistingdegradation, the greater will be the amount of organotin mercapto acidester required. Generally, as little as 0.25% total of the stabilizercomponents by weight of the resin, will give resistance to heatdeterioration.

There is no critical upper limit on the amount, but amounts above about10% by Weight of the resin do not give an increase in stabilizingeffectiveness commensurate with the additional stabilizer employed.Preferably, the amount is from about 0.5 to about 5% by weight of theresin.

The proportion of czor ,B-mercapto acid or mercapto alcohol is notcritical, and is sufficient to lessen early color deterioration of theresin. The mercapto acid or alcohol is not itself a stabilizer, and whenused alone is completely ineifectual. Consequently, it is remarkablethat as little as 0.1% of the mercapto acid or alcohol, by weight of theorganotin mercapto acid ester, markedly improves resistance to earlydiscoloration. Preferably, for optimum results, the amount of themercapto acid or mercapto al- 1O cohol is from about 0.25% to about 5%by weight of the organotin mercapto acid ester. The proportion ofmercapto acid or alcohol can be higher, 'but in amounts above 15% anyadditional advantage may not be commensurate with the amount added.

The mercapto acid or alcohol also improves clarity, particualrly whencloudiness-imparting additives are present, such as lubricants andimpact modifiers. In this event, more of the mercapto acid or alcoholmay be needed.

The stabilizer combination of the invention can be employed togetherwith other polyvinyl chloride resin stabilizers. The stabilizercombination of the invention in this event will be the major stabilizer,and the additional stabilizer will supplement the stabilizing action ofthe former, the amount of the stabilizer combination being within therange from about 0.25 to about 15 parts by weight per parts of theresin, and the additional stabilizer being in an amount of from about0.05 to about 10 parts per 100 parts of the resin.

Among the additional metallic stabilizers are included other organotincompounds, polyvalent metal salts of medium and or high molecular weightfatty acids and phenols, with metals such as calcium, tin, cadmium,barium, zinc, magnesium and strontium. The non-metallic stabilizersinclude phosphites, epoxy compounds, and the like. Epoxy compounds areespecially useful, and typical compounds are described in US. Patent No.2,997,454.

Generally, the stabilizer composition of this invention can be preparedby mixing the organotin mercapto acid ester with the mercapto alcohol ormercapto acid, either alone, or with any liquid lubricant or plasticizerto be added to the resin composition with the stabilizer.

The preparation of the polyvinyl chloride resin composition is easilyaccomplished by conventional procedures. The selected stabilizercombination is formed as above, and then is blended with the polyvinylchloride resins, or alternatively, the components are blendedindividually in the resin, using, for instance, a two or three rollmill, at a temperature at which the mix is fluid and thorough blendingfacilitated, milling the resin composition includng any plasticizer atfrom 250 to 375 F. for a time sufiicient to form a homogeneous mass,five minutes,

I usually. After the mass is uniform, it is sheeted off in the usualway.

The following examples in the opinion of the inventor representpreferred embodiments of this invention.

EXAMPLES 1 TO 7 A series of rigid or non-plasticized formulations wasprepared having the following composition:

noted in Table I below Six different mercapto acids and alcohols weretested. As controls, dibutyl tin bis (isooctylthioglycollate) and themercapto acids or alcohols were also used singly, in the same totalamount as the combinations (3.0 parts).

The stabilizer components were first mixed together in the proportionsindicated in a blender to form a stable homogeneous liquid solution,which was then mixed with the resin on a two-roll mill at 350 F. to forma homogeneous sheet, and sheeted off. Strips were cut off from thesheets and heated in an oven at 375 F. for two hours to determine heatstability. Pieces of each strip were removed at fifteen minute intervalsand affixed .to cards to shows the progressive heat deterioration. Asample of each composition was pressed for three minutes at 375 F. toobtain a press-polished sheet.

In all cases, the resins containing only mercapto acids and alcohols,and no organotin thioglycollate, turned a dark ochre on the mill, andwere therefore not subjected to the heat stability test. The appearanceof the other samples is reported in Table 1 below.

12 These compounds gave no improvement in resistance to earlydiscoloration, in combination with the dibutyltin diisooctylthioglycollate. Thus, synergistic improvement TABLE I Example Control 12 3 Stabilizer composition- Dibutyltin bis(isooctyl Dibutyltinbis(isooetyl Dibutyltin bis(isoocty Dibutyltin bis(isoootylthiothioglyeollate, 3.0 thioglyeollate), 2.97; tliioglycollate), 2.94;glyeollate), 2.97; thiomalio thiolactic acid, 0.03 thiolaetic acid, 0.06acid, 0.03

Time, minutes Color Color Color Color Initial (pressed ColorlessColorless Colorless Colorless.

polished sheet).

Light yellow Very light yellow Very light yellow Very light yellow.

30... d do do Do.

45 do Light yellow Light yellow Light yellow 60 Yeldlow with darkenedLiggit yellow, darkened Ligit yellow with darkened Light yellow withdarkened edges.

e ges. e ges. e ges.

75-.. do. Yellow darkened edges Yelilcw with darkened Yellow withdarkened edges.

e es.

90 Dark yellow, brown Dark yellow, brown Dark yellow with slight Dorkyellow with brown streaks. streaks. brown streaks. streaks.

10 Brown Brown Brown Brown.

120 Black Black. Black Black.

Example 4 5 6 7 Stabilizer eomposition Dibutyltin bis(isooetylDibutyltin bis(isoootyl Dibutyltin bis(isooetyl Dibutyltinbis(isoootylthio thioglyoollate), 2.07; thiosalicylie acid, 0.03

thioglyoollate), 2.91; amereapto lauric acid 0.00

thioglyoollate), 2.94; 2'mereapto ethanol, 0.06

glycollate). 2.97; B-mereapto propionic acid 0.03

Time, minutes Color Color Color Color Initial (pressed ColorlessColorless Colorless Colorless.

polished sheet).

l5 Very light yellow Very light yellow Very light yellow Very lightyellow.

45 Light yellow Light yellow Light yellow Light yellow.

60 Llgll? yellow, darkened Light yellow, darkened Ligit yellow, darkenedLight yellow, darkened edges.

e ges. et ges. e ges.

75 Yellow, darkened edges Yellow, darkened edges. Yellow, darkened edgesYellow, darkened edges.

90 Dagk ylgllow, brown Brownish yellow Brownish yellow Dark yellow,brown streaks.

s rea s.

105 Brown Brown Brown Brown.

120 Blavk Black Black Black.

The results clearly indicate that the aand [3- mercapto acids andmercapto alcohols greatly improve the resistance to early discolorationat 375 F. of polyvinyl chloride in resistance to early discoloration ofthe compositions of Examples 1 to 7 is rather remarkable; moving themercapto group away from the 0c and [3 position destroys the resinscontaining an organotin mercaptocarboxylic acid effect, and so doesesterification of the acid group. ester, i.e., dibutyltinbis(isooctyl-thioglycollate) as a heat A further stabilizer compositionwas prepared, using 1.0 stabilizer. The dilference between light yellowand very part of thioglycollic acid, and 99.0 parts of dibutyltindilight yellow during the first thirty minutes of heating is isooctylthioglycollate. This composition was not homoquite significant, sincethe material remaining on the rolls geneous, and dibutyltinthioglycollate separated out as a or in other processing equipment issmall, relative to the precipitate. This of course was what would beexpected, batch, and a very small difference in color intensity may fromUS. Patent No. 2,789,963, Example 1. Composispell the difference betweena colorless batch and one havtions of dibutyltin dilaurate with 2%thioglycollic, thiolacing a faint discoloration, due to this residualmaterial. tic and ,B-mercapto propionic acid were all incompatible Incontrast, w-mercapto acids other than uand fi-merand formedprecipitates. capto acids and all mercapto acid esters are ineffectivein Compositions using the resin formulation of Examples this respect.Thus, the oz and ,8 position of the mercapto 1 to 7, but substitutingdibutyltin dilaurate for the digroup and the free carboxylic acid groupeach contribute butyltin diisooctyl thioglycollate, and employingthiolacto effectiveness. tic acid mercaptoethanol and w-mercaptobutyricacid as The w-mercapto acid and mercapto acid esters shown in theadditional mercapto acid or alcohol component, were Table II below weremixed with dibutyltin di(isooctyl mixed into the polyvinyl chlorideresin composition. The thioglycollate), and blended with the same resinformularesin compositions were sheeted off, the sheets cut into tion asin Examples 1 to 7. The resin mixtures were sheeted strips, and thestrips subjected to the heat stability test, at off, and tested as inExamples 1 to 7, at 375 F. 375 F. The results obained are shown in TableIII.

TABLE II Stabilizer composition in parts by weight Dibutyltin bis(isooctylthioglycollate) 3.0

Dibutyltin bis(isooetylthioglycollate) 2.85; Dioctyl thiomaleate 0.15

Dibutyltin bis(isooetylthioglycollate) 2.88; Octyl Time (minutes) ColorColor Color Color Inltial (pressed polished sheet) Colorless Co orlessColorless Colorles 15 Yellow i Yellow Yellow.

30 do d0 do Do.

45 d0..- \'10 Do.

d0 .110 do Do.

Dark yellow, V Dark yellow, Dark yellow, Dark yellow,

darkened edges. darkened edges. darkened edges. darkened edges.

Brownish-yellow, Brownish-yellow, Brownish-yellow, Brownish-yellow,darkened edges. darkened edges. darkened edges. darkened edges.

Very dark brown Very dark brown Very dark brown Very dark br wn.

Black lack Black Black.

TABLE III I II III IV Stabilizer composition in parts by weightDibutyltin dilau- Dibutyltin dilau- Dibutyltin dilaurate, 2.94;Thiolaerate, 2.94; Mercaptorate, 2.94; w-Mercaptic acid, 0.06 ethanol,0.06 tobutyric acid, 0.06 Dibutyltin dilaurate, 3.0

Time (minutes) Color Color Color Color Initial (pressed polished sheet)Colorless Colorless Pale yellow Pale yellow. Dark yellow- Dark yellowBrown Medium brown.

Medium brown. Medium brown Medium brown Do. o 0 do Dark brown with blackedges.

Very dark brow Very;l dark bro ery1 dar Very) dark brown.

It is evident from the above results that the thiolactic acid,mercaptoethanol and wmercaptobutyric acid are each virtually equivalent,and do not impart any significant lessening of discoloration during thefirst thirty minutes of heating. In fact, at the conclusion of thirtyminutes of heating all of the samples are virtually identical, un-

The stabilizer combination was blended with the resin formulation on atwo-roll mill at 300 F., and worked five minutes, after which themixture was sheeted off. Strips were cut from the sheet and heated in anoven at 350 F., with samples withdrawn at fifteen minute intervals, cutfrom the strip and aflixed to a card. The

like the samples in Examples 1 to 7. The w-mercaptoresults are shown inTable IV.

. TABLE IV Control Example 8 Example 9 Stabilizer composition in partsby weight Dibutyltin diisooctyl Dibutyltin diisooctyl thioglycollate,3.0

Dibutyltin diisooctyl thioglycollate, 2.97; thiolactic acid, 0.03

thioglycollate, 2.85; thiolactie acid, 0.15

Time (minutes) C l r Color Color Initial (pressed polished sheet)Colorless with haze Colorless With barely detectable haze Clear andcolorless,

15 Yellow with haze. do D0.

do. Clear and very faint yellow tint Do.

0 do. Faint yellow tint Very faint yellow tint. 75 Dark yellow Withdarkened edges dn 90 Brownish yellow with darkened edgesdo- Do.

105 Very dark browndo Do,

120 Black Yellow tint Faint yellow tint.

butyric acid is substantially Without elfect, and the slight effectevidenced by the thiolactic acid and mercaptoethanol is apparent only inthe first fifteen minutes of heating.

@Accordingly, the aand s-mercapto acids and alcohols employed inaccordance with the instant invention are effective with the organotinmercapto acid ester stabilizers, and in this respect differ from othermercapto acids and alcohols, such as the w-mercapto compounds, but notwith other organotin stabilizers such as dibutyltin dilaurate, a typicaldialkyl tin dicarboxylate. With these the w, fland w-mercapto compoundshave virtually the same ineffectiveness.

EXAMPLES 8 AND 9 Two polyvinyl chloride resin formulations werepreparedemploying an impact modifier system in combination with polyvinylchloride resin. The impact modifier used was Blendexacrylonitrile-butadiene-styrene copolymer. This material imparts adistinct haze to the composition.

The formulation prepared was as follows:

Parts by weight Diamond 450, polyvinyl chloride resin homopolymer 150Wax E, lubricant 0.37 Blendex 401 18 Stabilizer combination shown inTable 1Vamount shown in Table IV.

It is evident that the thiolactic acid greatly lessens the initialdiscoloration during the first thirty minutes of heating and alsoimproves clarity, even in an amount as small as 1% by weight of thedibutyltin diisooctyl thioglycollate. When the amount is increased to5%, a clear composition is obtained, with a greatly improved resistanceto early discoloration, continuing through the first hour of heating.

EXAMPLES 10 AND 11 Polyvinyl chloride resin compositions were preparedaccording to the following formulation:

TABLE V Control Example Example 11 Stabilizer composition in parts byweight Dibutyltin diisooctyl Dibutyltin diisooctyl thioglycollate,thioglycollate, 2.85; Dibutyltin diisooctyl thioglyeollate, 3.0 2.94;thiolactic acid, 0.06 thiolactic acid, 0.15

Time (minutes) Color Color Color Initial (pressed polished sheet)..Colorless Colorless odorless, 1 do do Do. First barely noticeable yellowtint-. do. Do. Very faint yellow tint First barely noticeable yellowtint Do. Faint yellow tint. Faint barely noticeable yellow tint..--.First barely noticeable yellow tint. 7 do Faint yellow tint Barelynoticeable yellow tint. 9O Yellow tintdo- Faint yellow tint. 10% d0 Paleyellow Do. 120 --do do. Pale yellow.

It is evident that the thiolactic acid greatly improved the resistanceof the polyvinyl chloride resin to the development of an early yellowdiscoloration. In fact, in Example 11, the amount of the thiolactic acidwas suflicient to prevent development of any discoloration whatsoeverthrough the first forty-five minutes of heating, and even after one andone-half hours of heating, there is only a faint yellow discoloration.

' EXAMPLE 12 TABLE VI Control Example 12 Stabilizer composition in partsby weight Dibutyltin diisooctyl Dibutyltin diisooctyl thioglycollate,3.0 thioglycollate, 2.73; thiolactic acid, 0.27

Time (minutes) Color Color Initial (pressed Colorless and cloudy Clearand colorless.

polished sheet).

15 Pale yellow and cloudy. Do. 30.. Light yellow Do. 45.- .d Do.

-. First barely detectable yellow tint. 90 .-d0 Do.

Faint yellow tint.

12 -.do Pale yellow tint.

It is evident that the thiolactic acid not only clears up the cloudinessintroduced by the calcium stearate, but also greatly improves theresistance to early discoloration.

Having regard to the foregoing disclosure, the following is claimed asthe patentable and inventive embodiments thereof:

1. A polyvinyl chloride resin composition having an enhanced resistanceto early discoloration when heated at 350 F. comprising a polyvinylchloride resin, (a) at least one organotin mercapto acid estercontaining two radicals per tin atom selected from the group consistingof alkyl and cycloalkyl groups having from three to about thirty carbonatoms and at least one mercapto carboxylic acid ester group linked totin through a mercapto sulfur atom and having from three to about sixtycarbon atoms, and (b) a mercapto compound selected from the groupconsisting of ctand ,B-mercapto carboxylic acids and O0- and B-mercaptohydroxy carboxylic acids having from three to thirty carbon atoms, andOtand .B-mercapto alcohols having from two to about thirty carbon atoms,

having one of the formulae Ills RsCCXOH l SH and

in Formulae III and IV, X is selected from the group consisting of g andH2 in Formula III: R and R are selected from the group consisting ofhydrogen and organic radicals selected from the group consisting ofalkyl, aryl, cycloalkyl, alkenyl, cycloalkenyl, hydroxyalkyl, CH COOH,

| HSCHOOOH and -(CH COOH, wherein n is four or five; When one of R or Ris --(CH COOH, the other is hydrogen; when one of R or R is I HSCHCOOHthe other is hydrogen; when one of R or R is hydroxyalkyl, the other ishydrogen; and R and R can be taken together with 17 and cycloalkenyl; RR R and R can be taken together with wherein R and R are alkyl orcycloalkyl groups having from three to about thirty carbon atoms, Z is abivalent organic radicalhaving from one to about thirty carbon atoms,and R is an organic group derived from an alcohol having from one toabout four hydroxyl groups and from one to thirty carbon atoms, and m isan integer from one to four.

3. A polyvinyl chloride resin composition according to claim 1 whereinthe mercapto compound is a mercaptocarboxylic acid.

4. A polyvinyl chloride resin composition according to claim 1, whereinthe mercapto acid is thiolactic acid.

5. A polyvinyl chloride resin composition according to claim 1, whereinthe mercapto acid is fi-mercapto propionic acid. I

6. A polyvinyl chloride resin composition according to claim 1, whereinthe mercapto compound is a mercapto alcohol.

7. A polyvinyl chloride resin compositiong faccording to claim 1,wherein the organotin acid ester is fa dibutyl tin thioglycollate esterand the mercapto compound is an Ot-ml'CaptO carboxylic acid.

8. A polyvinyl chloride resin composition according to claim 1, whereinthe organotin acid ester is a dibutyl tin thioglycollate ester and themercapto compound is a fi-mercapto carboxylic acid. i,

9. A homogeneous liquid stabilizer composition for lessening earlydiscoloration of polyvinyl chloride resins due to heating at 350 F.,comprising (a) at least one organotin mercapto acid ester containing tworadicals per tin atom selected from the group consisting of alkyl andcycloalkyl groups having from three to about thirty carbon atoms and atleast one mercapto carboxylic acid ester group linked to tin through amercapto sulfur atom and having from three to about sixty carbon atoms,and (b) a mercapto compound selected from the group consisting of aandfit-mercapto carboxylic acids and uand B-mercapto hydroxy carboxylicacids having from three to thirty carbon atoms, and w and ,B-mercaptoalcohols having from two to about thirty carbon atoms, having one of theformulae (III) Iiis Rs-C-CXOH in Formulae III and IV, X is selected fromthe group consisting of II 0 and H2 in Formula HI: R and R are selectedfrom the group consisting of hydrogen and organic radicals selected fromthe group consisting of alkyl, aryl, cycloalkyl, alkenyl, cycloalkenyl,hydroxyalkyl, -CH COOH,

I HSCHCOOH and (CH COOH, wherein n is four or five; when one of R or Ris (CH ),,COOH, the other is hydrogen; when one of R and R is I HSCHCOOH the other is hydrogen; when one of R or R is hydroxyalkyl, the otheris hydrogen; and R and R can be taken together with to form a phenylring.

in Formula IV: R and R are selected from the group consisting ofhydrogen and organic radicals selected from the group consisting ofalkyl, aryl, cycloalkyl, alkenyl, cycloalkenyl and hydroxyalkyl; whenone of R or R is hydroi'ryalkyl, the other is hydrogen; R and R areselected from the group consisting of hydrogen and organic radicalsselected from the group consisting of alkyl, aryl, cycloalkyl, alkenyland cycloalkenyl; R R R and R can be taken together with to form aphenyl ring, a naphthyl ring, a cyclohexyl ring or a furfuryli'ring; themercapto compound being in an amount of from 0.1 percent to about 15percent by weight of the organotin mercaptd acid ester. 10. A stabilizercompositon in accordance with claim 9 wherein the organotin mercaptoacid ester has the formula Sn [S Z (COOR) I wherein R and R are alkyl orcycloalkyl groups having from three to about thirty carbon atoms, Z is abivalent organic radical having from one to about thirty carbon atoms,and R is an organic group derived from an alcohol having from one toabout four hydroxyl groups and from one to thirty carbon atoms, and m isan integer from one to four.

11. The stabilizer composition of claim 9 wherein the mercapto compoundis a mercapto carboxylic acid.

12. The stabilizer composition of claim 9 wherein the acid is thiolacticacid.

13. The stabilizer composition of claim 3 wherein the acid is,B-mercaptopropionic acid.

14. The stabilizer composition of claim 9 wherein the mercapto compoundis mercapto alcohol.

15. The stabilizer composition of claim 9 wherein the mercapto compoundis present in an amount of from 0.25 to about 5 percent by weight of theorganotin mercapto acid ester.

16. A stabilizer composition according to claim 9 wherein the organotinmercapto acid ester is a dibutyl tin thioglycollate ester and themercapto compound is an a-mercapto carboxylic acid.

17. A stabilizer composition according to claim 9 wherein the organotinmercapto acid ester is a dibutyl tin thioglycollate ester and themercapto compound is a fl-mercapto carboxylic acid.

20 References Cited FOREIGN PATENTS 9/1957 Great Britain. 8/1961 GreatBritain. 11/ 1961 Great Britain.

6/ 1962 Great Britain.

15 DONALD L. CZAJA, Primary Examiner V. P. HOKE, Assistant Examiner US.Cl. X.R.

39 3 9 3 Um'rlco S'lA'llCS r/l'ncm OFFICE f1" 1" (i 1 1 (I Clall I ll:MIA 1 la Ol CORRLC l lON Patent No. 3, 507,827 Dated April 21, 1970Inventor(s) Mark W. Pollock It is certified that error appears in theabove-identified patent and that said Letters Par -:11; are herebycorrected as shown below:

I" Column 2, line 44, "2,914,110" should be 2,914, 506 7 Column 4, line36, mercapcoz-ixelaic" should be --mercaptoazelaic Column 4, line 45,"acn" should be can Column 4, line 53, lsotrodecyP' should beisotridecyl Column 4, line 59, "'adiene-3-d" should be adiene-Z3-0lColumn 4, line 59, "cycloheptene-B-d" should be --cycloheptene-3-ol-;Column 5, line '7, "marcapto" should be mercapto Column 6, line 76 5,Formula No. 19, formula should read as follows:

H c,H,,-sn- CH2-CH,C-OCH2CH,OCH.,CH2OCCH2CH3 Column 7, line 4, FormulaNo. 21, should read C,,H ("3 H Column '1, line 11, Formula No. 22, S-CHCOOCH OH OH" should read S-CH COOCH CH OH I Column 10, line 22, "or"should read of Column 10, line 71, "shows should read show @[ii' useRENEW ssllr I J Attest:

Edward M. Fletcher, 3h

swam somnmm, Attestmg Officer Gonm'llssioner of Te. wil

